Fluid-cooled coaxial line terminator

ABSTRACT

An electrical coaxial line termination having greatly improved voltage standing wave ratio created by inserting a solid rod conductor axially within and connected to one end of a resistor, one end is connected to the inner conductor of the coaxial line. Preferably, the resistor is positioned within a logarithmically tapered horn which is connected to the outer conductor of the coaxial line at one end and is connected to the end of the resistor remote from the connection of the resistor to the inner conductor of the coaxial line.

United States Patent [72] inventors Leo Lesyk Walton Hills; James M. Lawson, Jr., Parma, both of Ohio 211 App1.No. 41,026 Y [22] Filed May 27, 1970 [45] Patented Jan. 11, 1972 73] Assignee Bird Electronic Corporation Solon, Ohio [54] FLUID-COOLED COAXIAL LINE TERMINATOR 3 Claims, 2 Drawing Figs.

[52] US. Cl 333/22 F, 333/81 A [51] Int. Cl l-l0lp 1/26 [50] Field of Search 333/22, 22 F,

[5 6] References Cited UNITED STATES PATENTS 2,968,774 1/1961 Rodriquez 333/22X 3,254,316 5/1966 Mcl lenry 333/22 3,324,424 6/1967 Barker.... 333/22 3,502,788 3/1970 A1bert.... 333/22 X 3,509,495 4/1970 Morton 333/22 Primary Examiner-Herman Karl Saalbach Assistant Examiner-Paul L. Gensler Altorney-McCoy, Greene & Howell ABSTRACT: An electrical coaxial line termination having greatly improved voltage standing wave ratio created by inserting a solid rod conductor axially within and connected to one end of a resistor, one end is connected to the inner conductor of the coaxial line. Preferably, the resistor is positioned within a logarithmically tapered horn which is connected to the outer conductor of the coaxial line at one end and is connected to the end of the resistor remote from the connection of the resistor to the inner conductor of the coaxial line.

FLUID-COOLED COAXIAL LINE TERMINATOR BRIEF DESCRIPTION OF THE INVENTION This invention relates to electrical devices for use in reflectionless terminations for coaxial transmission lines. More specifically, this relates to the discovery that the insertion of a solid rod conductor axially within and having one end connected to a cylindrical resistor of a line termination improves the electrical characteristics of the termination. The resulting combination behaves as a lossy load termination, i.e., exhibits' a band-pass characteristic and also has a low-voltage standing wave ratio (V.S.W.R.) at power frequencies (400 c.p.s. down to direct current). One of the advantages of this combination is that it can be tested and used at power frequencies. It can also be used as a calorimetric transfer device in which the power-absorbed can be determined at power frequencies by the change in temperature of a circulating coolant.

Still another advantage of this combination is that item be readily converted from a lossy" load to a conventional-type load by removing the axially positioned conducting rod. One of the significant features of this combination is that its bandpass characteristic can be adjusted by changing the diameter of the axially positioned rod.

Still another feature of this invention is the use of a solid Teflon tip on the end of the rod remote from the connection of the rod to the resistor, which tip prevents arcing from the rod to the resistor.

BRIEF DESCRIPTION OF THE DRAWINGS The embodiment of the invention illustrated in the accompanying drawings, forming a part of this specification, represents the best known mode of practicing the invention for effectuatingthe above objectives and certain other objectives having to do with details of construction and arrangements of parts which will become apparent as the description proceeds, this description being made by the use of reference numerals which indicate the parts throughout the views.

In the drawings:

FIG. 1 is a broken view in elevation, partly in section, showing the .line terminating device according to one illustrative embodiment; and

FIG. 2 is a view in section taken along the line 22 of FIG. 1 and looking in the direction of the arrows.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1, there is depicted in broken form a view in elevation partly in section of a coaxial line attenuator embodying this invention. Generally speaking, the attenuator is of the type disclosed in FIG. 6 of Stevens et al. US. Pat. No.

3,300,737. The features and advantages of the subject invention are achieved by axially positioning conducting rod 11 within the coaxial line attenuator 10. The details of the attenuator 10 are adequately described in the above-mentioned Stevens et al. Patent and the disclosure therein is hereby incorporated by reference.

Briefly, the termination 10, as viewed in FIG. 1, has its left end connected to a coaxial line by means of a cylindrical conducting member 12 which is connected to the outer coaxial conductor, not shown, by means of a snug fitting sleeve 13. The inner conductor of the termination 10 is connected to the inner conductor of the coaxial line by means of a cylindrical conducting member 15 mounted on a circular fluid barrier 16 by means of a nut and bolt assembly 17, 18, respectively. The threaded bolt 18 is actually an extension of a thimblelike conducting member 20 extending through fluid barrier 16, and receiving in the opposite end thereof a cylindrical resistor 22, the outer surface of which is covered with a resistive coating in a manner described in detail in the above-mentioned patent. The outer conductor of the line termination includes a logarithmically tapered horn 24 which is connected to and snugly fit within cylindrical housing member 26, and is connected by means of suitable sleeves 27, 28 and bolts 30 to conducting member 12. The right-hand end of horn 24 is connected to a resistor 22 by means of a cylindrical sleeve 32 which is received within the right-hand end of horn 24 and constitutes the right-hand terminal for the resistive coating.

A fiber or insulating tube 34 is positioned within and preferably has its axis coincident with the axis of resistor 22 for the purpose of directing fluid flow through the interior of resistor 22 in a manner described in detail in the above-men tioned patent. The termination 10 is provided with suitable coolant inlet fittings 36, 38 which are coupled to the insulating tube 34 and a suitable combination of coolant outlet fittings including a receiving chamber 39 defined by a cylindrical member 40 and an end cap 41 and outlet tubes 43, 44.

The conducting rod 11 is maintained with its axis coincident with the axis of insulating tube 34 and resistor 22 by means of a pair of insulating pins 46, 48 which are each of a length substantially equal to the internal diameter of the insulating tube 34. The left-hand end of rod 11 is threadedly engaged by means of threads 50 in a suitable hole in the thimblelike conducting member 20. Thus, the rod 11 is electrically connected to the inner conductor of the coaxial line, not shown, by means of conducting members 20 and 15.

The presence of rod 11 within the resistor 22 causes the line termination to have a low V.S.W.R. (voltage standing wave ratio) in the power frequency range and also causes the combination to exhibit a band-pass characteristic which is typical of the performance of a lossy load. The particular width of the band pass and its upper and lower limits are determined by the diameter of rod 11. One advantage of the low-loss characteris'tic at power frequency is that it facilitates testing of the line termination. Another advantage of this power frequency characteristic is that it makes possible both absolute or calorimetric and comparison or power testing.

With respect to the diameter of the rod, in two illustrative embodiments, rod diameters of five-eighths and one-eighth inch were employed within a resistor 22 having a diameter of 1.125 inches. The 43-inch diameter rod exhibited a band-pass frequency range from 600 to 1.600 mc.; whereas, the /e-inch diameter exhibited a frequency band pass from 200 to l,200 mc. Another embodiment of rod 11 having a %-inch diameter exhibited a band-pass frequency range of 400 to 1,300 me. In each instance, the rods were inserted within insulating tube 34 having an internal diameter of 0.725 inch. Water was employed as the coolant. Tests established that contamination of the water such as mixing the water with glycol or salt had no appreciable effect upon the electrical characteristics of the termination; whereas, without the rod, contamination of the coolant causes detrimental changes in the voltage standing wave ratio. Thus, the presence of the rod 11 increases the available frequency range of a line termination and provides it with a stable characteristic insensitive to coolant contamination. Preferably, the rod 11 is provided with a Teflon tip 54 which terminates in a point, and the presence of this Teflon tip prevents arcing from the rod 11 to the coolant fitting 36 and to the conducting end wall 31 of the line termination 10. Preferably, the Teflon tip point engages a recess in the end wall to provide mechanical support for one end of rod ll.

While several illustrative embodiments of the invention have been described in detail, it is understood that the concepts thereof may be utilized in various ways, numerous modifications and alterations being contemplated, it being understood that the embodiment shown in the drawing is given merely for the purpose of explanation and illustration without intending to limit the scope of the claims to the specific details involved.

What is claimed is:

1. A termination for a coaxial transmission line comprising:

a hom -shaped outer conductor;

resistance means including an elongated hollow ceramic dielectric member mounted coaxially within said outer conductor and having a resistive coating on one surface thereof, said member having an opening in one end thereof;

fluid conduit means including a tube projecting into said 2. A terminating device according to claim 1 wherein said opening for dehvering fluld coolant to the interior of said rod has its axis aligned with the axis of said resistance means.

member 831d tube havmg a Smaller cross Sumo than 3. A terminating device according to claim 1 wherein said said opening wherein said fluid coolant is exhausted from rod has one end electrically connected to said resistance said dielectric member between said tube and said 5 means. member; and

a conducting rod positioned within said conduit means. 

1. A termination for a coaxial transmission line comprising: a horn-shaped outer conductor; resistance means including an elongated hollow ceramic dielectric member mounted coaxially within said outer conductor and having a resistive coating on one surface thereof, said member having an opening in one end thereof; fluid conduit means including a tube projecting into said opening for delivering fluid coolant to the interior of said member, said tube having a smaller cross section than said opening wherein said fluid coolant is exhausted from said dielectric member between said tube and said member; and a conducting rod positioned within said conduit means.
 2. A terminating device according to claim 1 wherein said rod has its axis aligned with the axis of said resistance means.
 3. A terminating device according to claim 1 wherein said rod has one end electrically connected to said resistance means. 